Modeling dough

ABSTRACT

A modeling dough comprising gelled poly(vinyl alcohol), water and a filler provides a dough resistant to flaking, cracking, and crumbling. In the disclosed invention, the poly(vinyl alcohol) resin is gelled, thereby providing a water-based resin system that is not sticky yet very ductile. Prior to drying, the dough also exhibits the properties of bounceability and the ability to pick up newsprint. After the dough is air-dried, the poly resin serves to bind the components into a solid, durable product. The filler accounts for a large portion of the volume of the dough, so the overall volume is not greatly affected by water loss upon drying. The dough is water-based and easy to wash from skin, carpets, and other surfaces. Dyes and pigments can be easily incorporated into the formula. The dried product is sandable and paintable.

RELATED APPLICATION

This is a continuation-in-part of our prior U.S. patent application Ser.No. 07/734,951, filed Jul. 24, 1991 now U.S. Pat. No. 5,171,766. Theentire disclosure of the '951 application is incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to an improved water-based modeling doughfor use by children and artists in general. Specifically, the presentinvention relates to an improved water-based modeling dough for use bychildren and artists in general. Specifically, the present inventionrelates to an improved water-based modeling dough having a gelledpoly(vinyl alcohol) resin and a filler, which bind to form a matrix. Thepresent invention provides an improved water-based modeling dough whichforms a solid, lightweight, durable product upon drying.

BACKGROUND OF THE INVENTION

The present invention does not relate to oil-based clays comprisingnaturally occurring clays that are mined as rocks. Rather, the presentinvention relates to man-made, water-based modeling doughs.

Non oil-based modeling doughs are normally air-dryable and incorporatestarch as the filler. These doughs have a tendency to flake, crack, andcrumble in both the wet and dry stages. These doughs also shrinksubstantially upon drying. In other words, these doughs arecharacterized by poor plasticity, poor dry strength and substantialdrying shrinkage.

Plasticity is the property of a wet dough or clay that permitsdeformation by application of a relatively slight pressure and retentionof the deformed shape after release of the pressure. This propertydistinguishes the dough in its wet stage from its dry stage. When wet,starch-based modeling doughs have a low plasticity and have a tendencyto break apart during the molding or manipulating process. These doughsalso have a tendency to crack when dry and are not easily shaped in thedry state by sanding or filing. Furthermore, the artist cannot easilyadd wet dough to the existing dried sculpture. Finally, artists cannotcarve dried starch-based doughs.

Another problem inherent with water-based doughs is the loss of volume(shrinkage) upon drying. Because water accounts for a large portion ofthe volume of the dough in its wet stage, water loss upon drying resultsin a loss of volume in the resulting molded product.

One attempt to overcome the shrinkage problem has been to incorporatelarge proportions of filler in the dough mixture, but there is stillshrinkage because the volume decreases as the filler binds togetherafter drying. One commercially available children's dough, for example,shrinks about 20% upon drying despite its high filler content. In otherwords, a sculpture made with that dough can lose about 20% of its totalvolume upon drying. Moreover, the use of large proportions of filleraggravates the flaking, cracking and crumbling problem discussed above,and also tends to decrease the dry strength of the molded sculpture.

Discoloration upon drying is another problem associated with water-baseddoughs and is compounded by the dry shrinkage discussed above. As thevolume decreases, the concentration of the pigment increases and thecolor darkens.

Yet another problem associated with conventional water-based doughs isthat they are heavy and hard to manipulate. Dense, heavy doughs areawkward and the child or artist is limited in the types of shapes thatcan be created without the dough falling apart.

Finally, currently available water-based doughs are destructive totextiles, carpeting, furniture and other surfaces. They tend to stain asurface and are not easily removed by washing.

In light of the above problems, the need arises for a water-basedair-drying dough that is easily washed from textiles, carpeting andother surfaces. Furthermore, the water-based, air-drying dough must beable to incorporate dyes and pigments and not discolor upon drying.

SUMMARY OF THE INVENTION

The discovery of the present invention is that one may formulate asuperior modeling dough by combining gelled poly(vinyl alcohol) resin, afiller and water to form a cohesive water soluble resin system. Thewater evaporates upon drying to leave a gelled poly(vinylalcohol)-filler material that is both lightweight and durable.

In one preferred form, the composition of the invention includes fromabout 4% to about 15% poly(vinyl alcohol), from about 0.1% to about 2%gellant, from about 40% to about 60% water and from about 10% to about30% filler.

Optionally, the composition of the invention may include one or more ofa buffer, a defoamer, a wetting agent, a humectant, a preservative, andcolorants.

When the preferred fillers are used, the doughs disclosed have a densityof less than 0.48 g/cc. Previously known water-based doughsincorporating starch as the filler have a density of about 1.25 g/cc,and natural clays have densities of 2.50 g/cc. Thus, the dough disclosedby the present invention is substantially lighter than modeling doughsand clays previously available. Further, the doughs disclosed by thepresent invention have a very limited amount of dry shrinkage, areextrudable when wet, and are sandable, carvable, and paintable when dry.

Therefore, one general object of the invention is to provide alightweight water-based air-drying modeling dough that contains acohesive water-soluble resin system and that is resistant to flaking,cracking, and crumbling.

A further object of the invention is to provide a lightweightwater-based air-drying modeling dough that does not substantially shrinkin volume upon drying.

Another object of the invention is to provide a water-based air-dryingmodeling dough incorporating a gelled resin with a high degree ofplasticity, wet ductility, and extrudability, yet a low degree ofstickiness in the wet product.

Yet another object of the invention is to provide a water-basedair-drying modeling dough that is sandable and carvable after drying.

A still further object of the invention is to provide a water-basedair-drying modeling dough that enables the artist to add wet dough tothe existing dried sculpture.

An additional object of the invention is to provide a water-basedair-drying modeling dough with the ability to pick up newsprint.

Another object of the invention is to provide a water-based, air-dryingmodeling dough incorporating dyes, colorants and pigments and which doesnot discolor upon drying.

Yet another object of the invention is to provide a water-basedair-drying modeling dough with the ability to bounce.

And, another object of the invention is to provide a water-basedair-drying modeling dough that is more easily washed from skin,carpeting, textiles and other surfaces compared to other modelingcompounds.

Further and additional objects will appear from the description andappended claims.

DETAILED DESCRIPTION

To achieve the foregoing and other objects in accordance with thepurposes of the present invention, as embodied and broadly claimedherein, the modeling dough disclosed in the present invention comprisesfrom about 40% to about 60% water, from about 4% to about 15% poly(vinylalcohol) resin, from about 10% to about 30% filler and from about 0.2%to about 2% gellants.

A preferred formulation of the dough of the present invention comprisesfrom about 43% to 49% water, from about 8% to about 12% poly(vinylalcohol) resin, from about 25% to about 26% filler, and from about 0.15%to about 0.3% gellant.

The poly(vinyl alcohol) resin binds with the filler upon drying, therebyavoiding the flaking, cracking and crumbling problems associated withprior compositions. The poly(vinyl alcohol) gives the dough itsductility and plasticity qualities while wet.

However, employing poly(vinyl alcohol) as a resin can result in a doughthat is sticky and hard to manipulate. Therefore, a gellant, such as awater soluble borate salt, in an amount of from about 0.15% to about 2%by weight, is used to gel the resin substantially, eliminate stickiness,and impart wet ductility to the resulting dough. Preferably, the gellantis used in compositions of the invention in an amount of from about0.15% to about 0.30% by weight.

Most water soluble borate salts are acceptable. Sodium tetraborate isthe preferred gellant, however, because it also acts as a buffer tomaintain the pH of the system at a level high enough to permit gellingof the poly(vinyl alcohol). Other workable gellants include, but are notlimited to: resorcinol, catechol, gallic acid, 2-4-dihydroxy benzoicacid and congo red dye.

Poly(vinyl alcohol) as used in the present invention is a cream-coloredpowder which is soluble in water and insoluble in most organic solvents.It is made by the hydrolysis of poly(vinyl alcohol) and contains fromabout 1% to about 22% acetyl groups.

Poly(vinyl alcohol) may be partially or fully hydrolyzed. It varies inmolecular weight according to the length of the resin chain. Both thedegree of hydrolyzation and molecular weight independently affect thethermal stability of the dough.

The thermal stability of poly(vinyl alcohol) increases as both thedegree of hydrolyzation and molecular weight increases. The disclosedmodeling dough that is made with a more fully hydrolyzed grade ofpoly(vinyl alcohol) and/or a higher molecular weight of poly(vinylalcohol) has a better thermal stability than a dough made withpoly(vinyl alcohol) that is less hydrolyzed and/or has a lower molecularweight.

Thermal stability testing is done at 60° C. (145° F.) for ten days,because these conditions have been adopted by the paint and coatingsindustry as an approximation of three years of shelf-life. The doughshould show little change in consistency, functionality and color.

If the molecular weight of the poly(vinyl alcohol) is too low, the doughwill not pass thermal stability testing. However, if the degree ofhydrolysis is too high, the resulting dough may be thermally stable butwould be too crumbly and brittle and would not perform acceptably. Aproper balance is struck by either a medium molecular weight(85,000-146,000), partially hydrolyzed (87-89%) poly(vinyl alcohol) or anear fully hydrolyzed (96.5-97.5%) low/medium molecular weight(31,000-146,000) poly(vinyl alcohol). These resin grades are thepreferred resin grades because they impart better thermal stabilitycoupled with acceptable performance properties. Among the usefulpoly(vinyl alcohol) resins are those sold under the tradenames Airvol523 and Airvol WS42 by Air Products & Chemicals, Inc. and Elvanol 52-22by E. I. dupont de Nemours and Company. The poly(vinyl alcohol) resin ispreferably present in compositions of the invention in an amount of fromabout 4% to about 15% by weight of the composition. The poly(vinylalcohol) resin is more preferably present in compositions of theinvention in an amount of from about 8% to about 12% by weight of thecomposition.

If bounceability of the dough is a requisite feature of the product,then a lower molecular weight, partially hydrolyzed poly(vinyl alcohol)such as Airvol 203 or Airvol 205 should be used. This resin grade alsoproduces doughs that are especially resistant to cracking. However,doughs made with this resin grade have reduced thermal stability andwill have a shorter shelf-life.

Dry shrinkage is another problem inherent in water-based doughsdisclosed in the prior art and overcome by the present invention. Thepresent invention overcomes this problem by incorporating a filler thatbonds with the gelled poly(vinyl alcohol) resin to form an adequatematrix. The water evaporates upon drying without substantial shrinkageto the sculpture or other molded object. Workable filler, in the amountof 10 to 30 weight percent, include hollow composite microspheres, inerttalc, calcium carbonate, mica, clay or ceramic particles andcombinations thereof. Most preferred in compositions of the invention isa concentration of filler in an amount of from about 25% to about 26% byweight.

The hollow composite microspheres are the preferred filler primarilybecause of the low cost. They are functionally desirable because theyare lightweight (having density of about 0.13 g/cc) and lower thedensity of the modeling dough.

The hollow composite microsphere filler incorporated in the modelingdough disclosed by the present invention is especially helpful inpreventing the molded object or sculpture from shrinking upon drying.While the weight percent of water in the present invention is high (40%to 60%), the actual partial volume of water is relatively low due to therelatively high density of water (1.0 g/cc) and low density of themicrospheres. An even more preferred range of water content incompositions of the inventions is from about 43% to about 49% by weight.

As a result of these relative weights, the hollow microspheresconstitute the majority of the volume of the dough. The poly(vinylalcohol) and the microspheres bind together to give a sufficientstructural integrity for molding. Thus, when the water evaporates, thedough does not lose a large percentage of its total volume.

The preferred filler consists essentially of hollow compositemicrospheres of about 50 micron diameter and having a wettableparticulate coating. Microspheres with a larger diameter are workablebut may give the dough a grainy texture. Microspheres with a smallerdiameter may result in a heavier dough but result in a smoother texture.Thus, the choice of a particular size is determined by the desired endproperties.

The microsphere coating facilitates the wetting of the microspheres bythe liquid ingredients of the dough. The coating also contributes to thesmooth feel and inhibits stickiness in the final product, therebyallowing easy manipulation. The preferred coating is calcium carbonate.Other coatings include talc, alumina trihydrate, and titanium dioxide,as well as functional components such as pigments and dyes.

One preferred coated microsphere is sold under the tradename Dualite™M6001AE by Pierce & Stevens. M6001AE is an ultra-low density, resilient,polymeric microsphere coated with calcium carbonate. It is a lightweightfiller that reduces density of the dough and occupies the volume notattributable to water and resin. The resilient polymeric microspheresare shear stable and impact resistant, thus remaining intact underformulation conditions. Other hollow composite microsphere fillersuseful in the composition of the invention have densities ranging from0.10 to 0.75 g/cc, and include the wettable particulate coatingsdiscussed above.

Other workable microspheres are available in various sizes anddensities. Ceramic microspheres range in diameter from 15 to 40 micronsand have a density of about 0.7 g/cc. However, the ceramic microspheresgive the dough a grainier texture and a brownish coloring. Silicaalumina alloy microspheres range in diameter from 1 to 100 microns andhave densities ranging from 2.1 to 2.5 g/cc, depending upon the wallthickness. Plastic microspheres made from a variety of materials areavailable in sizes ranging from 10 to 1000 micron diameter and densitiesranging from 0.13 to 0.95 g/cc. Any of these materials, or combinationsof such materials, may be employed for the purpose of achievingparticular combinations of properties.

The preferred composition of the modeling dough disclosed by the presentinvention incorporates six additional optional components: (1) adefoamer; (2) a wetting agent or dispersant; (3) a humectant; (4) apreservative; (5) a colorant; and (6) a buffer.

A defoamer is used to eliminate air bubbles upon mixing of thecomponents, and such additives are readily available from numeroussources. The amount of defoamer is not critical, though such materialsare typically used in amounts of from about 1 to 2% by weight. BalabBubblebreaker 748, an aliphatic oil and surfactant mixture, or any otherof the commercially available defoamers are equally suitable.

The wetting agent promotes dispersion of the microspheres and of anyparticulate colorant during the mixing of the disclosed modeling dough,and such materials are well known. One preferred wetting agent is soldunder the tradename Nopcosperse 44 by Henkel, a nonionicpolyelectrolyte. The preferred weight percent of wetting agent is fromabout 0 to about 2%.

The humectant is not an essential component, but it is preferably addedto help plasticize the poly(vinyl alcohol). Without the humectant, thedisclosed modeling dough may be more brittle. The preferred humectantsare triglycerol and glycerin because they are superior plasticizers inthis system and produce a dough with a smooth texture. Alternative, yetsatisfactory, humectants are propylene glycols, poly(ethylene glycols)(i.e. Carbowax 200) and diethylene glycol. The humectant may be presentin an amount of from about 0 to about 20% by weight.

A desirable additive that increases shelf-life is a preservative, and awide variety of such materials is available commercially. One preferredpreservative is Kathon LX1.5, a 1.5% solution of isothiazolines. Anotherpreferred preservative is Nuosept 95. The preferred weight percent ofpreservative is from about 0.15% to about 0.75%.

If no colorant is used, the resulting dough is white. A white dough hasmany applications because it can be easily painted with water-basepaints. Also, white is an attractive color in itself and has manyapplications without the need for painting. If a colored dough isdesired, a variety of pigments and dyes may be used. Fluorescent doughsare especially attractive to children. Fluorescent pigments that workespecially well include those sold under the trade names Aurora PinkZ-11-3, Saturn Yellow Z-17N and Signal Green Z-18-3.

A buffer may also be added to raise the pH in some formulations. Whenthe pH is below 7.0, the poly(vinyl alcohol) does not gel properly. Ifboric acid is used as the gellant, the pH tends to drift and creates theneed for a buffer. Also, formulations using low molecular weight,partially hydrolyzed poly(vinyl alcohol) resins are acidic and require abuffer. However, one appropriate buffer is sodium tetraborate, which isalso the preferred gellant. None of the examples disclosed below containa buffer other than the sodium tetraborate gellant because the pH levelsare sufficiently high. Alternative buffers, when needed due to a pHbelow 7.0, include 2-amino-2-methyl-1-propanol and sodium bicarbonate.The preferred amount of this additive, when used, is from about 0 toabout 1% by weight.

EXAMPLES

While only four formulations are set forth below in the four examples,alternative formulations will be apparent to those skilled in the art.Such artisans will be able to modify the formula with an eye toward thedesired performance properties and intended use, both of which may varywidely. The evaluation of any single formulation is therefore inherentlysubjective.

When altering the formulas disclosed below it is important to maintain apH level near 7.5 or higher. Doughs with a pH below 7.0 may ungel andbecome sticky and difficult to handle. As stated above, a buffer mayalleviate this problem.

The modeling doughs disclosed by the present invention are made by firstdissolving the poly(vinyl alcohol) resin in water to form about a 20%solution. The solution must be heated (185° F.) to get the poly(vinylalcohol) to dissolve. Then, the rest of the liquid components, exceptthe gellant, are blended in a mixer. An aqueous solution of the gellantis added last. Agitation should be stopped before the microspheres areadded because they are very light and aerate easily. The mixture shouldbe covered before agitation is restarted. Once a homogenous, creamymixture is obtained, the gellant is added.

Sodium tetraborate, the preferred gellant, is dissolved in water to forma 2% to 4% solution. Higher concentrations require heat to dissolve thesodium tetraborate. The solution should be added dropwise and slowlyover the creamy mixture as it is blended. The amount of gellant added isdetermined by the preferred texture and softness of the final product.

The modeling doughs disclosed by the present invention have a dryingtime of about 24 to about 48 hours and a shelf-life (in the wet state)of about 2 years at room temperature.

Modeling doughs disclosed by the present invention were produced bymixing the following components, the amounts being expressed in weightpercent:

    ______________________________________                                        Example 1                                                                     Component            Amount                                                   ______________________________________                                        Airvol WS42          7.46                                                     medium/low molecular weight                                                   96.5-97.5% hydrolyzed                                                         water                54.57                                                    Dualite ™ microspheres                                                                          22.72                                                    sodium tetraborate   0.51                                                     Balab Bubblebreaker 748                                                                            1.10                                                     Nopcosperse 44       0.55                                                     glycerin             12.94                                                    Kathon LX1.5         0.15                                                                          100.00                                                   ______________________________________                                    

The modeling dough of Example 1 is not sticky and is easy to manipulate.It has a somewhat powdery texture. However, the dried structure isfairly brittle and the wet dough is not very ductile. The wet dough hasa density of 0.41 g/cc and a pH of 7.51.

    ______________________________________                                        Example 2                                                                     Component            Amount                                                   ______________________________________                                        Airvol 205           10.76                                                    medium/low molecular weight                                                   87-89% hydrolyzed                                                             water                56.79                                                    Dualite ™ microspheres                                                                          17.34                                                    sodium tetraborate   0.28                                                     Balab Bubblebreaker 748                                                                            1.78                                                     Nopcosperse 44       0.89                                                     triglycerol          12.01                                                    Kathon LX1.5         0.15                                                                          100.00                                                   ______________________________________                                    

The dough of Example 2 exhibits excellent bounceability, has excellentplasticity, is very ductile and is resistant to cracking. The drieddough is strong. However, the wet dough is not as thermally stable asthe dough disclosed in Example 1 and, therefore, has a shortershelf-life. The wet dough has a density of 0.45 g/cc and a pH of 7.66.

    ______________________________________                                        Example 3                                                                     Component            Amount                                                   ______________________________________                                        Airvol 523           8.60                                                     medium molecular weight                                                       87-89% hydrolyzed                                                             water                48.64                                                    Dualite ™ microspheres                                                                          25.50                                                    sodium tetraborate   0.28                                                     Balab Bubblebreaker 748                                                                            1.27                                                     Nopcosperse 44       0.64                                                     glycerin             14.92                                                    Kathon LX1.5         0.15                                                                          100.00                                                   ______________________________________                                    

The dough of Example 3 is fairly ductile, has good plasticity and thedried dough has good strength. The wet dough has a density of 0.37 g/ccand a pH of 7.48. Dough produced according to Example 3 has plasticitymeasured as from 2 to 2.5.

    ______________________________________                                        Example 4                                                                     Component            Amount                                                   ______________________________________                                        Airvol 523           11.88                                                    medium molecular weight                                                       87-89% hydrolyzed                                                             water                43.61                                                    Dualite ™ microspheres                                                                          25.37                                                    sodium tetraborate   0.16                                                     Balab Bubblebreaker 748                                                                            1.40                                                     Nopcosperse 44       0.71                                                     glycerin             16.52                                                    Kathon LX1.5         0.15                                                     Nuosept 95           0.20                                                                          100.00                                                   ______________________________________                                    

Following additional study and experimentation, the dough of Example 4was formulated and prepared. This dough was designed to reduce minorcracking problems that may arise as the dough dries. Cracking was foundto be reduced by increasing the percentage content of poly (vinylalcohol) in relation to the glycerin content. As a result of thisincreased poly (vinyl alcohol) content, the end product was strengthenedand any cracking associated with previous formulations was minimized.

In arriving at the formulation for Example 4, the ratio of resin toglycerin was increased. This increase produces a dough which is stifferthan the previous examples. For the formulation of Example 4, theplasticity was measured as 2.6 mm.

In addition, the formulation of Example 4 required less borate toachieve the desired gel strength for the dough. Further, a lower borateconcentration suitably served as a buffer for the composition. The pH ofthe formulation of Example 4 was measured at 7.8.

A further benefit of the formulation of Example 4 is that less water wasneeded to complete the composition. The lower water content isbeneficial in that it results in a drier, stiffer dough that dries in ashorter period of time upon use by the consumer. The dough of Example 4did exhibit a very minor amount of cracking when formed into large,thick pieces. However, the performance of the dough was more thansuitable for the intended applications.

All of the doughs disclosed are easily washed from skin, carpeting,textiles and other surfaces. In fact, the modeling dough disclosed bythe present invention acts to clean the skin if the dough is pressedagainst the skin and then removed. Similarly, the disclosed modelingdough exhibits the ability to pick up newsprint.

While specific weight percent ranges of the components of preferredcompositions have been set forth in this disclosure, the specificproportions of the components are not narrowly critical to the practiceof the present invention.

From the foregoing description and examples, it is apparent that theobjects of the present invention have been achieved. While only certainembodiments have been set forth, alternative embodiments and variousmodifications will be apparent to those skilled in the art. These andother alternatives are considered equivalents and within the spirit andscope of the present invention.

What is claimed:
 1. A water-based moldable modeling dough composition comprising poly(vinyl alcohol), water, a gellant, and a filler, said composition having a pH of about 7.0 or greater, and said filler consisting essentially of plastic microspheres.
 2. The composition of claim 1, wherein said plastic microspheres have a wettable particulate coating.
 3. The composition of claim 2, said plastic microspheres having a density of from about 0.10 to about 0.75 g/cc.
 4. The composition of claim 1, wherein said poly(vinyl alcohol) is at least partially hydrolyzed.
 5. The composition of claim 1, wherein said poly(vinyl alcohol) is substantially fully hydrolyzed.
 6. The composition of claim 1, further comprising a buffer.
 7. The composition of claim 6, wherein said buffer is selected from the group consisting of sodium tetraborate, sodium bicarbonate, 2-amino-2-methyl-1propanol, and mixtures thereof.
 8. The composition of claim 1, wherein said gellant is a water soluble borate salt.
 9. The composition of claim 1, wherein said gellant is sodium borate.
 10. The composition of claim 1, wherein said gellant is a sodium tetraborate.
 11. The composition of claim 1, further comprising a defoamer.
 12. The composition of claim 1, further comprising a wetting agent.
 13. The composition of claim 1, further comprising a humectant.
 14. The composition of claim 13, further comprising, by weight, from about 0 to about 20 percent humectant.
 15. The composition of claim 14, wherein said humectant is selected from the group consisting of glycerin, triglycerol, propylene glycol and poly(ethylene glycols).
 16. The composition of claim 1, further comprising a colorant.
 17. The composition of claim 1, further comprising a preservative.
 18. A water-based moldable modeling dough composition comprising, by weight: from about 4% to about 15% poly(vinyl alcohol), from about 40% to about 60% water, from about 10% to about 30% filler, from about 1% to about 2% defoamer, from 0% to about 2% wetting agent, from about 0.1% to about 2% gellant, from 0% to about 20% humectant, from 0% to about 4% colorant, and from 0% to about 2% preservative, and said filler consisting essentially of plastic microspheres.
 19. The composition of claim 18, wherein said plastic microspheres have a wettable particulate coating.
 20. A water soluble moldable molding dough composition comprising, by weight, of from about 8% to about 12% poly(vinyl alcohol), from about 0.15% to about 0.3% sodium tetraborate, from about 25% to about 26% coated plastic microspheres, and from about 43% to about 49% water.
 21. The composition of claim 20, wherein said poly(vinyl alcohol) is at least partially hydrolyzed.
 22. The composition of claim 20, wherein said coated plastic microspheres have a wettable particulate coating.
 23. The composition of claim 22, wherein said wettable particulate coating of said plastic microspheres is calcium carbonate. 